HF combiners are used to combine mobile radio signals from different mobile radio bands, i.e. having different frequency ranges, to allow the mobile radio signals to be transmitted to an antenna mast via a shared cable to the antennas. A cable, also referred to as a feeder cable, is costly to manufacture due to the fact that it must have very good electrical properties (for example, with regard to dielectric losses). For this reason, attempts are made to transmit as many different mobile radio bands as possible via one feeder cable. Such a combination, or separation of mobile radio bands, is achieved using HF combiners. An HF combiner includes multiple signal line terminals that are connected to the various base stations. A base station receives a digital data stream, conditions it, and outputs it in an HF signal. The HF combiner combines HF signals of different frequencies from various base stations, and outputs them to a common terminal to which one end of the feeder cable is connected. The electrical functional units are connected at the other end of the feeder cable. The term “electrical functional units” is understood to mean not only the antennas themselves, but often also other components such as phase shifters, remote electrical tilt (RET) units, and dual tower mounted amplifiers (DTMAs). To allow operation and control of these further components of the electrical functional units, the particular base station also outputs a supply voltage (DC signal) and control signals (AISG signals). These antenna interface standard group (AISG) signals are transmitted at a frequency of 2.176 MHz, using an on/off keying method. Data rates of 9.6 kbps, 38.4 kbps, or 115.2 kbps, for example, may thus be achieved. The bandwidth of an AISG signal is preferably 200 kHz or less. The level of the on/off keying signal is +5 dBm (on signal), for example, and −40 dBm (off signal), for example.
Different filter paths are used in order for the HF combiners used to be able to transmit different mobile radio bands (different frequency ranges) at the individual signal line terminals to a common terminal to which the feeder cable is connected. This also ensures that signals that are received from a feeder cable are output to the correct signal line terminals. The signals to be sent from the base station may be transmitted via the same feeder cable that also transmits the signals to be received by the base station. However, different feeder cables, and thus different combiners, may also be used here for uplink and downlink. The filter paths are implemented in particular as band-pass filters, for which reason a DC signal and an AISG signal, which are necessary for controlling the above-mentioned electrical functional units, cannot be transmitted via these filter paths. For this reason, there are bypass lines that run outside the filter paths. The DC signal and the AISG signal are transmitted via these bypass lines. The bypass lines are outcoupled at the signal line terminals and coupled back in at the common terminal. Low-pass filters are provided here so that the particular HF signals of the mobile radio bands are also not outcoupled.
A base station has in particular two terminals. The MAIN signal is output or received at one terminal, and the DIV signal is output or received at another terminal. Both signals are phase-shifted by 90°, and are output or received, for example, by different dipoles of a vector dipole or dipole square. The frequency range is the same. However, the base station outputs an AISG signal at only one of the terminals.
In previous HF combiners from the prior art, individual signal line terminals are fixedly connected to the common terminal via bypass lines. In this case, DC signals and AISG signals can be transmitted only from a signal line terminal to the common terminal. Since a signal line terminal, due to the filter path to which it is connected, is used for connecting only one mobile radio band, various HF combiners are necessary to be able to transmit the AISG signals from each base station, via the feeder cable, to the electrical functional units to be controlled. This complicates manufacture of the HF combiners, and there is always the risk that faulty cabling will occur in setting up a mobile radio site, and the mobile radio site cannot be placed in operation.
In principle, consideration could be given to connecting the particular signal line, in which a DC signal is initially present, to the common terminal via a corresponding low-frequency outcoupling. However, here as well the problem would arise that for the case that the base stations are operational in a different time sequence and output a DC signal in a different time sequence, the interconnection of the signal line terminal to the common terminal would be faulty. In this case, the HF combiner also would no longer correct this interconnection when an AISG signal from another base station, which is not allowed until later, is then suddenly present at a different signal line terminal.
Aspects of the present technology, therefore, provide an HF combiner that is suitable for setting up a mobile radio site, even though MAIN signals or DIV signals from different base stations are present at its signal line terminals, and the particular signal line terminal at which an AISG signal is present is not defined beforehand.
The object is achieved by an HF combiner, by an HF combiner arrangement, and by a mobile radio site. Refinements of the HF combiner and refinements of the HF combiner arrangement are also contemplated.
The HF combiner according to example non-limiting embodiments includes a housing on which a common terminal and n signal line terminals (where n≥2) are situated. The n signal line terminals are connected and/or coupled to the common terminal within the housing via one of n filter paths in each case. The filter paths are in particular band-pass filters via which the mobile radio signals may be transmitted from the particular signal line terminal to the common terminal, or from the common terminal to the particular signal line terminal. In addition, a circuit board arrangement is provided. The circuit board arrangement is used for transmitting the outcoupled low-frequency signals (DC signal and AISG signal). For this purpose, the circuit board arrangement has a common terminal contact that is galvanically connected to the common terminal via a low-pass filter. In addition, the circuit board arrangement has n signal line terminal contacts, each of the n signal line terminal contacts being galvanically connected to the particular signal line terminal via a low-pass filter. In the simplest case, the terminal contacts are soldering points or plugs on the circuit board arrangement. The n signal line terminal contacts are hereby connected or connectable to the common terminal contact via n bypass lines. These bypass lines converge at the common terminal contact. Furthermore, there is an electronics unit that has a control device, a detector device, and at least n signal line switching devices. Each of these signal line switching devices includes a first switching unit. One of these switching units is situated in each of the n bypass lines, the switching units upon actuation being designed to disconnect or connect the particular surroundings line, in the latter case the signal line terminal contact in question being electrically connected to the common terminal contact. An AISG signal, which is present at the signal line terminal contact in question, is then transmitted to the common terminal contact. The transmission takes place in a conversion-free manner. This means that the AISG signal is not converted via additional modems (signal converters) into a different protocol. The bypass line for transmitting the AISG signal between the signal line terminal contact in question and the common terminal contact is therefore modem-free. The transmission takes place in this case preferably in a completely passive manner. This means that the signal is not changed, i.e. not amplified, for example. The connection between the signal line terminal contact in question and the common terminal contact is preferably low resistance. The detector device, which preferably includes n signal line detector devices, is connected or coupled either to the particular signal line terminal contact, or in each case between one of the n signal line terminals and the first switching unit. The detector device, in a BTS operating state, is designed to detect whether an AISG signal is present at one of the n signal line terminal contacts. For such a detection, the control device or the detector device is designed to control the first switching unit in the particular one of the n bypass lines in such a way that the first switching unit electrically connects the particular one of the n signal line terminal contacts, at which the AISG signal has been detected, to the common terminal contact. The AISG signal (low resistance) is transmitted from the signal line terminal contact in question to the common terminal contact by means of this electrical connection.
It is particularly advantageous that a detector device is provided with which an AISG signal can be detected at one of the n signal line terminal contacts. This result is then used to relay this AISG signal via the particular first switching unit to the common terminal contact, so that the signal is available at the common terminal. In this case, it does not matter whether the AISG signal is supplied to the first or second or third signal line terminal of the HF combiner. A BTS operating state is understood to mean that the HF combiner is connected to the base stations. The particular signal line terminals are therefore (at least indirectly) connected to the connections of the base stations, whereas the common terminal is connected to the feeder cable. The HF combiner is therefore situated “on the base” and not “on top of the antenna mast.”
A combiner having bypass lines is also disclosed in US 2017/257207 A1 and is connected to corresponding ports. A “bias tee” separates each of the bypass lines into an AISG line and a DC line, only AISG signals being transmitted via the AISG line and only DC signals via the DC line. In contrast to the solution according to example non-limiting embodiments, in which the detector device detects an AISG signal, in this case only detection of a DC signal takes place. If a DC signal is detected, the DC line is connected to the common terminal. In contrast, the AISG line associated with the same port is not connected electrically to the common terminal, as in the solution according to example non-limiting embodiments, but is galvanically separated by two modems. A first modem converts the AISG signal on the AISG line, which modem comprises an OOK modulation (on-off keying), into a TTL signal. The second modem converts the TTL signal back into an AISG signal and outputs it at the common terminal. The use of such modems means that no electrical connection is established for transmitting the AISG signal between the respective port and the common terminal.
The detector device can detect the presence of an AISG signal via a galvanic connection or via a (capacitive or inductive) coupling. This is described by the wording “connected” or “coupled.”
In one preferred embodiment of the HF combiner according to example non-limiting embodiments, the detector device is additionally connected or coupled either to the common terminal contact or between the common terminal and the n signal line switching devices. The detector device preferably has a common detector device. The detector device is designed to detect whether a DC signal is present at one of the n signal line terminal contacts. The detector device is also designed to detect whether a DC signal is present at the common terminal contact. When the control device is started, i.e. in particular when it is first supplied with power following a de-energised state, it assumes a starting operating state. From this starting operating state the control device may switch either into the BTS operating state or into an ANT operating state. In the BTS operating state, the control device changes over when the detector device detects a DC signal at one of the n signal line terminal contacts. In contrast, the control device changes over to the ANT operating state when the detector device detects a DC signal at the common terminal contact. The HF combiner according to example non-limiting embodiments may thus be universally used. It independently detects whether it is situated at the base stations, or on top of the antenna mast for the electrical functional units. Thus, only one HF combiner is necessary, which independently detects its particular location and purpose of use and appropriately adjusts its functionality. The ANT operating state is understood to mean that the HF combiner is connected to the electrical functional units. The particular signal line terminals are therefore directly connected, for example, to the connections of the antennas. An indirect connection may result from connecting the signal line terminals to the connections of single-band DTMAs or dual-band DTMAs, which in turn are connected to the antennas. The common terminal is hereby connected to the feeder cable. The HF combiner is therefore situated “on the antenna mast” and not “below on the base stations”.
As discussed at the outset, the base stations include at least two terminals. In a first terminal the MAIN signal is output or received, and in a second terminal the DIV signal is output or received. Both signals are present in the same frequency range, but phase-shifted by 90° relative to one another. For this reason, the two signals cannot be transmitted via the same feeder cable. Therefore, at least two HF combiners are required, which are connected to different feeder cables. Due to the corresponding transmission power outputs, these HF combiners preferably have a cavity design. The housing includes a housing base, the circuit board arrangement spaced apart from the housing base, and a circumferential housing wall between the housing base and the circuit board arrangement, thus delimiting a corresponding receiving space. For each filter path, at least one resonator inner conductor is provided that is galvanically connected to the housing base of the housing and extends in the axial direction from the housing base in the direction of the circuit board arrangement, and ends at a distance from the circuit board arrangement and/or is galvanically separated therefrom. The individual filter paths in which at least one resonator inner conductor is situated in each case are separated (decoupled), at least partially, from one another by a wall that is galvanically connected to the housing and extends in the direction of the circuit board arrangement and preferably is likewise galvanically connected thereto. Such a housing is preferably manufactured in an (aluminium) (pressure) casting process. Alternatively or additionally, a milling process may also be used. The individual HF combiners are then also closed with a cover assembly.
Since the MAIN signal and the DIV signal of a base station must be transmitted via two different HF combiners, in one refinement according to example non-limiting embodiments an HF combiner arrangement is described. This HF combiner arrangement includes a first and a second HF combiner having a cavity design. To reduce costs, according to example non-limiting embodiments the use of such housing covers has been dispensed with. The first and the second HF combiner are placed one on top of the other, wherein the circuit board arrangement electrically or electromagnetically separates the receiving space of the first HF combiner from the receiving space of the second HF combiner, and conversely. In particular, the end-face sides of the housing walls of the two HF combiners rest one on top of the other, wherein the circuit board arrangement separates the respective receiving spaces from one another. In this way an HF combiner arrangement may be provided in a particularly cost-effective manner, and in each case has n signal line terminals for the MAIN signal from n mobile radio bands, and n signal line terminals for the DIV signal from n mobile radio bands. On the other hand, there are two common terminals for connecting two feeder cables, which in turn are connected to the electrical functional units on the antenna mast. A design using strip conductor technology or microstrip conductor technology would also be possible.
The HF combiner according to example non-limiting embodiments and the HF combiner arrangement according to example non-limiting embodiments are used in mobile radio sites. A mobile radio site is understood to mean the combination of base stations, HF combiners, feeder cables, and electrical functional units (DB-DTMA, for example), in addition to the actual antenna elements on the antenna mast. Such a mobile radio site preferably includes at least two of the HF combiners according to example non-limiting embodiments or at least one of the HF combiner arrangements according to example non-limiting embodiments. In addition, n base stations are provided which are operable in different mobile radio bands. For example, different mobile radio standards (LTE, UMTS, GSM, for example) may also be used. Each of the n base stations includes at least two signal terminals, the n base stations being designed for transmitting and/or receiving a MAIN signal at a first signal terminal, and the n base stations being designed for transmitting and/or receiving a DIV signal at a second signal terminal. The first signal terminals of the n base stations are electrically connected to the n signal line terminals of the first HF combiner or of the first HF combiner of the first HF combiner arrangement. On the other hand, the second signal terminals of the n base stations are electrically connected to the n signal line terminals of the second HF combiner or of the second HF combiner of the first HF combiner arrangement. A first feeder cable at its first end is electrically connected to the common terminal of the first HF combiner or to the common terminal of the first HF combiner of the first HF combiner arrangement. A second feeder cable at its first end is electrically connected to the common terminal of the second HF combiner or to the common terminal of the second HF combiner of the first HF combiner arrangement. As discussed above, appropriate electrical functional units may be connected at the second end of the feeder cables.
Regardless of when the particular base station outputs its AISG signal, this signal is switched through by the HF combiner according to example non-limiting embodiments to the corresponding feeder cable. This AISG signal is therefore available at the second end of the particular feeder cable, and may be used for controlling the electrical functional units.